<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <div class="input-num">
            <button @click="sub">-</button>
            <span>{{ num }}</span>
            <button @click="add">+</button>
        </div>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <script>
        var app=new Vue({
            el:"#app",
            data:{
                num:1,
            },
            methods:{
                sub:function(){
                    if(this.num>0){//this调用本对象的num
                        this.num--
                    }else{
                        alert("最小了")
                    }
                   
                },
                add:function(){
                    if(this.num<10){
                        this.num++
                    }else{
                        alert("最大了")
                    }
                    
                }
            }
        })
    </script>
</body>
</html>